1. Technical Field of the Invention
This invention relates generally to wireless systems and more particularly to determining position within a wireless system and/or tracking motion within the wireless system.
2. Description of Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks to radio frequency identification (RFID) systems. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, radio frequency (RF) wireless communication systems may operate in accordance with one or more standards including, but not limited to, RFID, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof. As another example, infrared (IR) communication systems may operate in accordance with one or more standards including, but not limited to, IrDA (Infrared Data Association).
Depending on the type of RF wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, RFID reader, RFID tag, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network.
For each RF wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the receiver is coupled to the antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives inbound RF signals via the antenna and amplifies then. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signal into baseband signals or intermediate frequency (IF) signals. The filtering stage filters the baseband signals or the IF signals to attenuate unwanted out of band signals to produce filtered signals. The data recovery stage recovers raw data from the filtered signals in accordance with the particular wireless communication standard.
As is also known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts raw data into baseband signals in accordance with a particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna.
In most RF applications, radio transceivers are implemented on one or more integrated circuits (ICs), which are inter-coupled via traces on a printed circuit board (PCB). The radio transceivers operate within licensed or unlicensed frequency spectrums. For example, wireless local area network (WLAN) transceivers communicate data within the unlicensed Industrial, Scientific, and Medical (ISM) frequency spectrum of 900 MHz, 2.4 GHz, and 5 GHz. While the ISM frequency spectrum is unlicensed there are restrictions on power, modulation techniques, and antenna gain.
In a particular application, millimeter wave (MMW) communications are used in public safety applications to detect a metal object on a moving person. This can be accomplished because millimeter wave signals penetrate clothing, plastics, and fabrics, but are reflected by metal objects. The responses of the MMW signals are captured and processed utilizing a statistical model to detect the metal object.
In radar applications, RF signals are used to detect the relative distance of an object. In general, when the receiver and transmitter are in the same location, the received power declines as the fourth power of the range, which can be use to determine the distance to an object. The transmission of the RF signals may be polarized to reduce interferences and/or to better detect certain objects. For instance, circular polarization is used to minimize the interference caused by rain; linear polarization for better detection of metal surfaces; and random polarization for better detecting fractal surfaces. Alternatively, the radar signals may be FM modulated to improve distance detect.
In IR communication systems, an IR device includes a transmitter, a light emitting diode, a receiver, and a silicon photo diode. In operation, the transmitter modulates a signal, which drives the LED to emit infrared radiation which is focused by a lens into a narrow beam. The receiver, via the silicon photo diode, receives the narrow beam infrared radiation and converts it into an electric signal.
IR communications are used in video games to detect the direction in which a game controller is pointed. As an example, an IR sensor is placed near the game display, where the IR sensor detects the IR signal transmitted by the game controller. If the game controller is too far away, too close, or angled away from the IR sensor, the IR communication will fail.
Further advances in video gaming include three accelerometers in the game controller to detect motion by way of acceleration. The motion data is transmitted to the game console via a Bluetooth wireless link. The Bluetooth wireless link may also transmit the IR direction data to the game console and/or convey other data between the game controller and the game console.
While the above video gaming technologies allow video gaming to include motion sensing, it does so with limitations. As mentioned, the IR communication has a limited area in which a player can be for the IR communication to work properly. Further, the accelerometer only measures acceleration such that true one-to-one detection of motion is not achieved. Thus, the gaming motion is limited to a handful of directions (e.g., horizontal, vertical, and a few diagonal directions).
Therefore, a need exists for improved motion tracking and positioning determination for video gaming and other applications.